Initially, my goal was to see if I could feed the fish Lactobacillus casei shirota with varying amounts of fructooligosaccharides and measure the concentration in their feces. I assumed (and was going to verify) that the more fructooligosaccharides I added, the higher the concentration would be found in their fecal matter. Unfortunately, one fish didn't survive and the other won't eat the pellets I feed it (he literally spits them out). I also wanted to identify a similar bacteria already resident in the digestive tract and compare its concentration as I fed the fish the Lactobacillus casei shirota.
At the very least, I can show that the Lactobacillus casei shirota survived its digestive tract and could be isolated and identified (assuming 16s is positive). The biochemical tests I performed on fecal sample colony I isolated (g+ rod cat neg) matched 10 unique tests. However, there is a common bacteria found in fish called Erysipelothrix rhusiopathiae that shares many similar characteristics with Lactobacillus casei shirota. So many of the tests like indole, catalase etc. are the same. The morphology differs slightly under the microscope, but I'm personally not able to differentiate between the two in practice yet. Erysipelothrix rhusiopathiae is, however, supposedly set apart form Lactobacillus spp. by its positive H2S production on TSI. I only performed this test one time for each and I saw no positive signs of H2S. Also, literature states that it produces acid but -no gas- in lactose and glucose. My sample produced gas, so that's another strike against Erysipelothrix rhusiopathiae, however, it needs to be repeated and verified. Below is a photo of the lactose test of the wild sample on the left vs. the control Lactobacillus casei shirota. I'm not sure the camera could pick up the gas bubbles, but I still have these samples for verification.
